High resolution electron microscope autoradiography on negative stained specimens

1973 ◽  
Vol 35 (1) ◽  
pp. 67-74 ◽  
Author(s):  
N. M. Maraldi ◽  
G. Biagini ◽  
P. Simoni ◽  
R. Laschi
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Electron Microscope Autoradiography ◽  
Resolution Electron ◽  
Microscope Autoradiography ◽  
High Resolution Electron Microscope

Scintillation and autoradiographic studies on 63 nickel uptake in Pseudomonas tabaci

1984 ◽  
Vol 69 (1) ◽  
pp. 87-105
Author(s):  
R.H. Al-Rabaee ◽  
D.C. Sigee
Keyword(s):  
Acetic Acid ◽  
Electron Microscope ◽  
Physical Development ◽  
Bacterial Cells ◽  
Electron Microscope Autoradiography ◽  
Resolution Electron ◽  
Nickel Uptake ◽  
Microscope Autoradiography ◽  
High Resolution Electron Microscope ◽  
Silver Grains

Scintillation studies on the uptake of 63Ni2+ by Pseudomonas tabaci demonstrate an incorporation of approximately 2.5 nmol per 10(10) bacterial cells, in medium containing 12 nmol (8.3 microCi) per ml. Over 80% of the incorporated Ni2+ is lost from the cells during washing, fixation and dehydration with ethanol. The remaining insoluble (bound) 63Ni2+ has the highest level in cells fixed in acetic acid/ethanol (0.4 nmol/10(10) cells), with smarter amounts in paraformaldehyde- and glutaraldehyde-fixed cells. The radioactive level in aldehyde-fixed cells represents a total Ni2+ uptake of about 10(−18) g or 10(4) atoms per cell. Light- and electron-microscope autoradiography corroborated the scintillation studies in demonstrating a higher retention of label by cells fixed in acetic acid/ethanol, possibly reflecting a higher retention of medium Mr proteins with this type of fixation. High-resolution electron-microscope autoradiography involving gold latensification with physical development demonstrated a clear localization of silver grains to the central nucleoid region (seen most clearly over the discrete nucleoid of aldehyde-fixed cells) and within this to the chromatin (seen most clearly over the condensed chromatin of acetic acid/ethanol-fixed cells). It is suggested that the incorporated 63Ni2+ labels mainly central, genetically inactive DNA, while peripheral, actively transcribing DNA has little associated radioactivity. The pattern of cation association seen in this bacterium shows a number of close similarities to the situation seen in dinoflagellate cells.

An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

Computer-Controlled Hrem Alignment Using Automated Diffractogram Analysis

1990 ◽  
Vol 48 (1) ◽  
pp. 532-533
Author(s):  
G.Y. Fan ◽  
O.L. Krivanek
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
The Other ◽  
Full Information ◽  
Resolution Electron ◽  
Skilled Operator ◽  
Automatic Alignment ◽  
High Resolution Electron Microscope ◽  
Computer Controlled ◽  
Recorded Image

Full alignment of a high resolution electron microscope (HREM) requires five parameters to be optimized: the illumination angle (beam tilt) x and y, defocus, and astigmatism magnitude and orientation. Because neither voltage nor current centering lead to the correct illumination angle, all the adjustments must be done on the basis of observing contrast changes in a recorded image. The full alignment can be carried out by a computer which is connected to a suitable image pick-up device and is able to control the microscope, sometimes with greater precision and speed than even a skilled operator can achieve. Two approaches to computer-controlled (automatic) alignment have been investigated. The first is based on measuring the dependence of the overall contrast in the image of a thin amorphous specimen on the relevant parameters, the other on measuring the image shift. Here we report on our progress in developing a new method, which makes use of the full information contained in a computed diffractogram.

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